Use Beer Calculus and switch the batch size to 2.5 or 1 gallon or whatever. I've found it particularly useful especially when the amount of malt extract I want is an odd amount. You can adjust it accordingly and see where your gravities are. Same with the Hops.
Mr. Malty has a yeast pitching calculator that will tell you how much yeast you need to pitch for smaller batches. For 2.5 gallon, I still use one vial or package. I don't have the links handy at the moment, I'm at work and they're saved on my home laptop.
Edit: Yes, this is a wonderful hob... er.. obsession. I love doing the smaller batches because I can make more varieties and have a case of each, rather than two cases of something. Plus, smaller batches let me do full boils, get the most from the hops.